1. Field of the Invention:
This invention relates to optical systems using a gradient-index lens, particularly one having a radial gradient of refractive index.
2. Description of the Related Art:
Recently image pickup elements and integrated circuits of smaller size and higher performance have been developed. This trend is reflected in increasing demands for further reducing the bulk and size of the optical system and also further improving the image quality. In accompaniment with it, however, the difficulty of solving the aberrational problem is increasing, and further development has not been fruitful.
To solve the problem, gradient-index lenses come to attract attention. Particularly the radial gradient of refractive index is expected to further develop systems of the class described. In the present state of art, however, no method of its effective application is yet established. As the related art, mention may be made of U.S. patent application Ser. Nos. 800,553, 810,670, 847,670, 847,236.